This invention relates to a feed control system employed to feed sticky fluids with a netative, non-linear shear rate. More specifically, this invention relates to the use of a shaded pole motor system comprising an A.C. motor and D.C. brake for driving a peristaltic pump to supply a uniform feed of sticky, thixotropic fluid to dishwashers, chemical reactors, and the like.
Typical fluids, particularly when used in connection with dishwashers, include soaps, detergents, rinse additives, etc. Fluids having both thixotropic and linear flow properties may be pumped simultaneously or separately.
Present commercially available pump devices for feeding fluids to dishwashers include venturi, diaphragm, bellows, and piston pumps. Both the bellows and piston pumps employ a mechanical type of adjustment to vary the length of stroke in the bellows or piston. However, these types of devices are accurate only to within about 5%-15%, and are expensive; also, their check valves tend to foul up when pumping the sticky fluids.
What is required is a control system which can pump small amounts (at least about 1-10 ml/minute) of thixotropic fluids to a dishwasher, chemical reactor and the like, within reasonable limits of about .+-.1%-2%, even though the load on the pump is non-linear due to the thixotropic nature of the fluids.